The Rangers left-back, who had been expected to make his first start of the Gordon Strachan era against the Croatians in place of the suspended Steven Whittaker, missed training at Hampden yesterday after aggravating a pre-existing knee complaint and is touch and go for the final World Cup qualifier of the campaign.
The Scotland boss reacted to the news by calling up Steven Hammell of Motherwell as cover, the veteran getting the nod ahead of Dundee United teenager Andrew Robertson.
"Lee is not great," Strachan said yesterday. "We will take a look at it and if there is any danger that he is going to miss next week then he is not going to play.
"He came to us with a wee bit of a problem. It got better after Friday - he only trained in the afternoon because we were looking after him - but it stiffened up the longer the night went on and it was stiff this morning. We have not got adequate cover on the defensive side so we had to call someone up."
Strachan's opposite number Igor Stimac has his own problems. Defeat to Belgium in Zagreb means they will face a play-off to reach the World Cup finals, and four players - including big hitters such as Luka Modric, Mario Mandkukic and Vedran Corluka - are just one booking away from a suspension.
"Maybe the temptation for the coach is to make sure they don't get booked and that means they might not play," said Strachan.
"But they have still got Eduardo, [Ivica] Olic and [Nikica] Jelavic who can. So that isn't bad."
Whether he makes it or not, Wallace's club manager Ally McCoist last night heaped plaudits upon the player. "Lee has been immense for us and it says a lot that Gordon is keeping him in the squad," said the Rangers boss. "The fact Gordon got him on in Macedonia - and he did well - is great."